


In Theory

by lizlybear



Category: Merlin (TV)
Genre: Alternate Universe - Modern Setting, Anal Sex, Best Friends, Blow Jobs, Bottom Merlin, M/M, Porn with Feelings, Porn with a tiny plot, Rimming, Shower Sex, Top Arthur, misquoting disney
Language: English
Status: Completed
Published: 2017-01-30
Updated: 2017-01-30
Packaged: 2018-09-20 18:17:27
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,683
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9504995
Author URL: https://archiveofourown.org/users/lizlybear/pseuds/lizlybear
Summary: Merlin has this theory about shower sex, he wants/needs to test it out. His best friend is a perfect lab rat.





	

Merlin didn’t know how it came to this, but here he was, asking his best friend to try out shower sex with him. Arthur’s mouth drops open when he blurts out the question. He looks at Merlin, blinks owlishly and closes his jaw with an audible click. Merlin’s hands grow damp and he feels himself turn a fiery red. Holy fuck, what the hell had he been thinking?! Oh wait, he knows exactly what he had been thinking. His mind flashes back to the beginning.

A few weeks ago he was bored as fuck, browsing through his favourite porn sites, looking for something new to wank to. He stumbled upon a video of two guys having the most delicious looking shower sex. After that he was hooked, watching every available video he could find to clench his thirst for his newly developing kink.

One night he was lying on his bed, slowly stroking his dick, and mentally going through his spank bank for the right person to star in this wank session. He ended up imagining Arthur, his best friend and long time crush.

In his mind they were in the shower together, Arthur had just finished fingering him and he was roughly turned around and pushed against the tiles. The fantasy came to an abrupt halt because Merlin suddenly realised that Arthur was shorter than him, so he wouldn’t be able to pound Merlin into the wall properly.

After trying out a few different positions in his head, he came to the conclusion that either he would have back pain because of him bending down, or Arthur would have back pain because he had to lift Merlin’s full weight, or Arthur would have to stand on a box.

Fast forward three weeks and a lot of unsatisfying wank fantasies later, Merlin knew something had to be done. He needed to get it out of his system. It had to be Arthur. He would have to spin it in a way so that it looked like it was just an experiment. Most importantly, Arthur could never ever find out about his crush.

Years ago, when Merlin came out, Arthur had asked him if he was in love with him, because that would make him the most cliché gay guy in the world. Merlin had denied it and had laughed it off. He had shoved the crush away, into the darkest corner of his mind.

 And as he watched Arthur pick up men and women, falling in and out of love easily, he’d wondered if it would have been the same for him. Would they have had a hot, fast affair? After which they would have moved on, still being best friends? Merlin liked to think so, but in his heart he knows he would’ve fallen in love with Arthur even more. Arthur would have broken his heart. No use in wondering, he had made his bed so to speak.

He had asked Arthur to come over for lunch. Now they were sitting across from each other, Arthur talking about how incompetent his new assistant is. Merlin takes a bite out of his sandwich and tries to focus on the story instead of Arthur’s lips. Now that he has decided to ask Arthur for sex, he can’t stop thinking about it. The very moment Arthur is finished with his food, Merlin blurts out the question, explaining the how and why in what seems to be one long sentence.

And now he sits at the table with sweaty palms waiting for Arthur to react.

For a moment the kitchen is completely silent. Merlin wipes his hands on his jeans. Then Arthur starts talking in a high pitch, he pauses, scrapes his throat and starts again. “Let me get this right. Your fantasy sex position doesn't work out in your head and you want to really try it out because you can’t wank properly anymore? And the reason you’re asking me for this is because our height difference is perfect for it?”

Merlin takes a deep breath. “That’s the gist of it, yeah.”

“So it’s not because you have a raging hard-on for my perfect body?” Arthur sits back with a smug look on his perfect face and looks him in the eye. “Or because you’ve been in love with me for years and you decided to ask me out in a very round-about way?”

Merlin is shocked. What the hell? Arthur can’t possibly know, he had always been so careful!

Merlin decides to play it cool. He smirks confidently and drawls out theatrically, “Yes, Arthur, that’s exactly it. I’ve been in love with you for years and this is the only way I can have you.” He lets the words hang for a second. “God, your ego is unlimited. Don’t be a dick and just answer the question. I can always ask Percy, you know.”

“I’ll do it. No need to bring Percy into this. When would you like to conduct your little experiment?”

Yes! Hook, line and sinker. _Merlin Emrys for the win_. “Tonight? Around nine?”

“That won’t work, I have a game tonight. What are your plans tomorrow?”

“Ehm, I have nothing on all day, why?”

“If we’re really going to do this, I want to take my time for it. So I’ll be here tomorrow afternoon around two. Do not prepare yourself. I want to see you come apart on my fingers before I fuck you stupid.”

Arthur shoves his chair back and stands up. He seems indecisive for a moment. Merlin curiously watches him as he steps toward Merlin, stopping beside him. Merlin takes a deep breath and looks up, just in time to see Arthur leaning down. Arthur slides his hand around the back of Merlin’s neck, pulling him upwards while simultaneously pressing his lips against Merlin’s. Tonguing the seam, asking for entrance. For a second Merlin forgets how to breathe. Then he opens his mouth and the kiss turns filthy in an instant, their tongues battling for dominance. Merlin’s hands scramble to take hold of the edge of the table.

Arthur releases him, smirking down. “Sealed with a kiss.” He winks. “See you tomorrow.”

Merlin hears the door slam and sits in his chair blinking rapidly and his heart thudding loudly. Sweet Lucifer, how the fuck did he think he could handle this? He’s wrecked from just one kiss. He lifts a trembling hand to his lips. He is _so_ fucked.

 

*****

 

Saturday afternoon arrives and Merlin is not pacing his small living room. He isn’t. There’s nothing to be nervous about. It’s going to be a wish-fulfilling afternoon. Then he’ll move on, and nothing will change between them. He nods to himself. Yes, nothing will change. Maybe if he keeps repeating it, he might start believing it.

Everything’s ready, he glances at the clock and takes a deep breath when he sees that he has half an hour left. He showered and cleaned himself thoroughly this morning. He went out and bought water based lube and condoms. He also acquired a plastic box which he placed just outside the shower cubicle. Just to be entirely sure, he checked and it held his weight, so it should be able to hold Arthur’s.

He looks at the clock and nervously checks everything again. Lube, condoms, towels and box. He stares at the box for a moment and can’t help the smile that breaks out at imagining Arthur’s expression when he realises he has to stand on the box if he can’t make it work.

He slouches down on the couch and waits impatiently. He fiddles with the remote while watching a lion chasing a gazelle on screen. Just as the lion closes in and goes for the throat, he hears the door to his apartment open.

Taking a deep breath, he sits up, and runs a hand through his hair. _Show time._ Arthur comes in and drops himself next to Merlin on the couch. He sits too close and Merlin’s senses are overdosed with everything Arthur: the spicy sweet smell of Versace, minty fresh toothpaste, a hint of bitter coffee, and last but not least something musky that is uniquely Arthur.

The scent makes his dick stand to attention, a heat curling in his underbelly. He pulls in a shuddering breath and turns to look at Arthur. Arthur has a knowing look on his face that irritates the hell out of him.

 “So, how do we sta—” He can’t complete his sentence because Arthur is kissing him. Merlin moans and opens his mouth. The kiss seems to go on forever and when Arthur finally pulls back they are both out of breath.

“First,” Arthur says, “we get the edge off, because you’re on the verge of coming in your pants like a teenage boy.”

Merlin splutters and Arthur’s smirk is infuriating.

“Off with your pants!”

“Really, Arthur? Disney quotes?” Merlin questions while pulling off his jeans and boxers.

Arthur’s response is muffled because he is pulling his shirt over his head, but Merlin can hear the laugh in his voice when he says, “Shut up, you love Disney.”

Once they’re both naked, Arthur pushes Merlin back onto the couch. He slides his hands over Merlin’s calves, stroking the insides of his thighs, parting them before settling in between them. Merlin hisses when his cock comes into contact with Arthur’s impressive, but only slightly bigger erection. Arthur lowers himself further, putting pressure on their dicks.

Arthur kisses down Merlin’s chest and shuffles backwards on the couch until he can rest Merlin’s legs on his shoulders. He then skillfully sucks down the tip of Merlin’s cock. Merlin moans loudly and bites his lip. If Arthur could smile with a mouthful, he would. Licking around the head, he tongues the foreskin. The taste of pre cum explodes on Arthur’s tongue and Merlin suddenly has a tight grip on Arthur’s hair.

Arthur winches and pulls off, Merlin takes his hand out of Arthur’s hair. “Sorry, shit. That was… please continue.”

He gives Merlin a grin, kisses the tip and moves further down to spend several minutes worshipping Merlin’s balls. He can tell Merlin is really enjoying it by the white-knuckled grip he has on the couch cushions. He rubs a dry fingertip over Merlin’s entrance, and he can feel a muscle spasm go through Merlin’s whole being.

Encouraged by this, he shifts Merlin’s arse and tongues the rim of his hole. He’s treated to the beautiful sight of Merlin gasping for air. Arthur drops one of Merlin’s legs, so he has easier access to Merlin’s tight hole.

He feeds one of his fingers to Merlin who enthusiastically lavishes them with saliva. He is now pushing his tongue in and out of Merlin’s hole, adding a soaked finger and hooking it just right. Merlin loses it, he grabs Arthur’s hair and pulls at it, letting him know he’s about to come. Throwing his head back, his hole clenches down on Arthur’s finger and his stomach muscles contract. His cock jumps and he cums all over himself.

Arthur sits up and wipes his mouth, grinning like an idiot. He swipes a finger through the mess on Merlin’s stomach and licks it off with a flourish. Merlin groans at the sight, drags Arthur down and hesitates a moment before kissing him. The kiss is slow and wet, and it makes Merlin’s toes curl. Arthur eventually pulls back and rests his head on Merlin’s shoulder. Arthur’s erection feels hot and heavy against Merlin’s thigh.

He makes a grab for it, but Arthur sits up and shakes his head. “No, I’m saving that. We still have some experimenting to do.”

Merlin nods. Arthur stands up. “Lube?” Merlin points towards the table. “Wow Merlin, good to know a perfect rim job renders you speechless.”

“Yeah… Wait, what? No, Jeez, who said it was perfect? It was adequate, you utter prat!”

Arthur sighs and shakes his head. “Uh huh, sure Merls, ‘adequate’. Keep telling yourself that.”

Merlin falls back into the cushions and throws an arm over his face, trying to hide a grin. Hearing Arthur's snort, he knows he didn’t succeed.

The couch cushions dip under Arthur’s weight. Arthur settles between his thighs. Slicking up his fingers, he pulls Merlin towards him. Arthur lifts up Merlin’s delectable bum until it’s spread wide and his for the taking.

Merlin looks up at Arthur and immediately wishes he hadn’t, because Arthur’s whole focus is on Merlin. His dick twitches under Arthur’s intense scrutiny and he squirms. Trying to hide his sudden shyness, Merlin snarks, “Growing old here, fucking _get on_ with it!”

Without lifting his eyes Arthur answers. “Patience is a virtue, Merlin. You know, the whole ‘all good things to those who wait’ crap.” He slides the first finger in, quickly followed by the second finger. Arthur hooks them just right, making Merlin’s cock jump.

He’s now scissoring two fingers into Merlin’s hole. It feels so full and yet not full enough. Merlin is moaning and babbling little confirmations, pushing back on Arthur’s fingers. It feels delicious and his dick is making a valiant effort to come back to life.  He is so ready. He wants it, no he _needs_ it.

His movements must have betrayed his need somehow, because Arthur squeezes the base of Merlin’s cock and pulls his fingers back. Merlin lets out an unsatisfied groan, but Arthur shushes him and slaps his bum.

Arthur stands up, grabbing the lube, and he holds up a condom. “I’m clean. You’ve seen my test results. I trust you’re clean as well. But if you really want it, we’ll use it.”

Merlin thinks for a second before grabbing it and tossing it back on the table. Arthur smiles and takes his hand, urging Merlin along, and pushing him towards the tiny bathroom.

Merlin opens the cabin door and turns the shower on. The stall looks very small next to Arthur’s broad shoulders. He hopes the shower can fit the two of them. While they wait for the water to heat up, Arthur places sweet kisses on Merlin’s shoulder, making his way up to his neck. Merlin slides a hand into Arthur’s hair, and captures his lips in an open mouthed kiss. His other hand finds his way to Arthur’s firm arse cheeks. Stroking over them before putting his nails in one of the cheeks, loving the way it makes Arthur moan.

Arthur pulls him close and strokes a hand over his back, down to his butt. He teasingly slips a finger into Merlin’s loose, sensitive hole. Merlin pushes back onto the finger. Arthur huffs out a laugh against Merlin’s lips. “So fucking eager.”

Merlin grunts and pulls Arthur back into the kiss. There’s almost no room between them. Their cocks are tightly pressed together, and the pre cum makes for the sweetest friction. He blindly reaches his arm into the shower to check the temperature. It’s hot, and ready. _He’s_ hot and ready _._

He steps away from Arthur and gets into the shower. _This is it_ , he thinks. Weeks and weeks of daydreaming coming true. He adjusts the heat, turning around only to find Arthur inches away from him. He stumbles back, grabbing Arthur to steady himself.

“I swear, you’re like a skittish colt sometimes.” Arthur shakes his head, grinning from ear to ear. “Are you sure your little scenario didn’t work out because you can’t keep your limbs under control?”

“Shut up, I didn’t expect you to be so close.”

“This shower isn’t exactly big _Mer_ lin.” Arthur pushes forward until Merlin is crowded against the wall.

His move successfully leaves Merlin out of the water spray, and Arthur with all the water cascading down on his broad shoulders and muscled arms. It plasters his hair against his skull. It should look ridiculous, but instead Arthur looks like the cover model for a swimsuit magazine.

Merlin’s eyes roam over the chiselled chest, the noticeable abs, the strong thighs and his gorgeous looking cock. It stands to attention with a slight curve to the right, the pinkish head glistening with more than just water.

Merlin licks his lips. Looking up, he sees Arthur’s eyes darkening in arousal. Merlin shivers, and he isn’t even that cold.

Arthur brings their faces together and proceeds to kiss him senseless. Merlin is hyper aware, every slick slide of wet skin against his own makes him groan into the kiss. Arthur wedges a thigh in between his legs and lets his hands drop to Merlin’s hips. Arthur’s dick nudges his abs and Merlin can feel his stomach muscles contract.

“Are you ready to start your silly experiment?” Arthur mumbles against Merlin’s lips.

 _Finally!_ Merlin thinks as Arthur slips a hand over his bum and to the back of his thigh. He can feel himself being lifted up. The cool, solid press of the tiles steadies him and makes his nipples harden. His other leg is being hauled up as well, he feels Arthur’s cock slide past his balls and over his hole before dipping into it. The head catches on the rim and Arthur adjusts his grip. The new angle lets Merlin sink further down onto his cock.

Merlin leans his head back against the tiles and sighs. He feels so fucking full. Arthur’s breath hitches when Merlin shifts, and Merlin takes a moment to enjoy the small noises Arthur is making. Arthur shudders and tightens his hands on Merlin’s hips, keeping him in place.

As if to distract himself, Arthur nuzzles and licks Merlin’s collarbone, lifting his head enough to brush his nose against the column of Merlin’s neck, and bites his earlobe.

The slight burst of pain makes Merlin clench his hole as he tightens his legs around Arthur’s waist. Arthur must like that response, because he does it again. Merlin grabs Arthur’s hair and pulls him into a kiss, which turns hot and heavy within seconds.

When Arthur starts moving, he makes gravity work for him. Instead of him fucking up into Merlin he lifts Merlin up and then lets him drop. Somewhere in the back of his mind, Merlin realises that Arthur doesn’t seem to have any problems catching his weight. He is very impressed, but it also means that his theory is about to be proven wrong. In this instance, he is happy to be wrong.

With the next drop Arthur moves into it and manages to hit Merlin’s prostate. Merlin bites his lip but can’t keep the moan from spilling out. Arthur gives him a smug grin and starts putting his back into the thrusts. With every upward thrust he hits the bundle of nerves. Merlin’s breath becomes erratic. He’s biting back moans. He looks down to see his cock leaking a steady stream of pre cum mixing with the water.

“Touch yourself,” Arthur grunts out.

Merlin hastens to comply and he disentangles his hand from Arthur’s hair to take a hold of his dick. He slips his thumb over the leaking head and he groans. Arthur picks up the speed of his thrusts. Merlin strokes become wild and within moments he feels a white-hot heat spreading through his body. All his muscles contract and he comes all over Arthur’s wet abs.

Arthur’s grip adjusts again, holding Merlin’s hips in a bruising grip. Arthur is effectively pounding  him into the wall, chasing his own release. With every thrust upward the air is forced out of Merlin and he has to tighten his legs as to not be thrown off balance. He fucking loves it.

Merlin drags his fingers through the mess dripping down Arthur’s abs, sliding them further down. He lets his index finger rest against his rim pushing slightly against Arthur’s dick. Seconds later, Arthur let’s out a breathy moan and pushes in as deep as he can, pumping his hips twice more before coming deep inside.

Arthur drops Merlin’s legs and slowly pulls out. He wraps an arm around Merlin’s waist and drags him under the warm water. He proceeds to kiss Merlin soundly and pulls back with a smacking noise.“How was that for shower sex? Did it play out the way you thought, or should we conduct some more experiments? Because I volunteer.”

Merlin gives him a satisfied grin. “I do believe some more experiments will be necessary.” He turns the shower off.

Afterwards, once they are both dry, they cuddle up on the couch. Arthur yawns and says, “So, when are you going to confess to the crush you’ve had on me for years?”

Merlin tries to turn around to look at Arthur but he holds him firmly with his back against his chest. “Crush? What crush? Don’t be weird.”

“Please Merlin, Gwaine spilled the beans weeks ago. I just don’t understand why you’d ask for this instead of just asking me out on a date.”

“I don’t want to be your flavour of the week, Arthur. I want… everything and I didn’t think you were up for that. And uh, I really did want to do this experiment.”

“Okay. I’m in, let’s do this. The full monty.”

Arthur finally allows him to turn around. Merlin uses his new found freedom to push Arthur flat against the couch. “No take backs. This means you’re stuck with me,” he says, staring straight into Arthur’s eyes.

“Now who’s the weirdo? If you’d been paying attention, you’d know I've had a thing for you for years now. Why do you think my father and sister keep asking you to join our weekly family dinners? And no, it’s not because you're my best friend. It’s because they think we’ve been dating for 5 years.”

“That actually makes a lot of sense.”

Arthur laughs and pulls Merlin down into a filthy, open mouthed kiss. “I’m glad you asked me for your experiment,” he whispers against Merlin's lips.

Merlin smiles. “Me too.” He snuggles against Arthur’s chest. He’s grateful that he stumbled across the shower porn. He’s even more grateful for Arthur’s insane arm muscles. Most of all he’s grateful that he’s going to have this for the rest of his life.  

 

Fin

**Author's Note:**

> I hope you enjoyed reading this. I would very much like to know what you thought of it. :)


End file.
